Allotropes Some elements exist in several different structural
forms, these are called allotropes.

For more information on Murray Robertson’s image see Uses and properties facts below.

Polonium

Discovery date

1898

Discovered by

Marie Curie

Origin of the name

Polonium is named after Poland, the native country of Marie Curie, who first isolated the element.

Allotropes

α-Po, β-Po

84

[209]

Fact box terminology

GroupElements appear in columns or ‘groups’ in the periodic table. Members of a group
typically have similar properties and electron configurations in their outer
shell.

PeriodElements are laid out into rows or ‘periods’ so that similar chemical behaviour is
observed in columns.

BlockElements are organised into blocks by the orbital type in which the outer electrons are
found. These blocks are named for the characteristic spectra they produce:
sharp, principal, diffuse, and fundamental.

Atomic NumberThe number of protons in the nucleus.

Atomic Radius/non -bonded (Å)based on Van der Waals forces (where several isotopes exist, a value is presented for
the most prevalent isotope). These values were calculated using a multitude of
methods including crystallographic data, gas kinetic collision cross sections,
critical densities, liquid state properties, for more details please refer to
the CRC Handbook of Chemistry and Physics.

IsotopesElements are defined by the number of protons in its
centre (nucleus), whilst the number of neutrons present can vary. The
variations in the number of neutrons will create elements of different mass
which are known as isotopes.

Melting Point (oC)The temperature at which the solid-liquid phase
change occurs.

Melting Point (K)The temperature at which the solid-liquid phase
change occurs.

Melting Point (oF)The temperature at which the solid-liquid phase
change occurs.

Boiling Point (oC)The temperature at which the liquid-gas phase change
occurs.

Boiling Point (K)The temperature at which the liquid-gas phase change
occurs.

Boiling Point (oF)The temperature at which the liquid-gas phase change
occurs.

SublimationElements that do not possess a liquid phase at atmospheric pressure (1 atm) are described
as going through a sublimation process.

Density (g cm-3)Density is the mass of a substance that would fill
1 cm3 at room temperature.

Relative Atomic MassThe mass of an atom relative to that of Carbon-12.
This is approximately the sum of the number of protons and neutrons in the
nucleus. Where more than one isotope exists the value given is the abundance
weighted average.

Key Isotopes (% abundance)An element must by definition have a fixed number of protons in its nucleus, and
as such has a fixed atomic number, however variants of an element can exist
with differing numbers of neutrons, and hence a different atomic masses (e.g.
12C has 6 protons and 6 neutrons and 13C has 6 protons and 7 neutrons).

CAS numberThe Chemical Abstracts Service registry number is a
unique identifier of a particular chemical, designed to prevent confusion
arising from different languages and naming systems (where several isotopes
exist, a value is presented for the most prevalent isotope).

Murray Robertson is the artist behind the images
which make up Visual Elements. This is where the artist explains his interpretation
of the element and the science behind the picture.

Natural Abundance

Where this element is most commonly found in nature.

Biological Roles

The elements role within the body of humans, animals
and plants. Also functionality in medical advancements both today and years
ago.

Appearance

The description of the element in its natural form.

Uses and properties

Uses and properties

Image explanation

An image based on Luna E-1, the first spacecraft of the Soviet ‘Luna’ programme. Later Luna spacecraft carried ‘Lunokhod’ rovers to the moon. These were the first rovers to explore the moon’s surface and were powered by polonium.

Appearance

A silvery-grey, radioactive semi-metal.

Uses

Polonium is an alpha-emitter, and is used as an alpha-particle source in the form of a thin film on a stainless steel disc. These are used in antistatic devices and for research purposes.

A single gram of polonium will reach a temperature of 500°C as a result of the alpha radiation emitted. This makes it useful as a source of heat for space equipment.

It can be mixed or alloyed with beryllium to provide a source of neutrons.

Biological role

Polonium has no known biological role. It is highly toxic due to its radioactivity.

Natural abundance

Polonium is a very rare natural element. It is found in uranium ores but it is uneconomical to extract it. It is obtained by bombarding bismuth-209 with neutrons to give bismuth-210, which then decays to form polonium. All the commercially produced polonium in the world is made in Russia.

Atomic data terminology

Atomic radius/non -bonded (Å)Based on Van der Waals forces (where several isotopes
exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties,for more details please refer to the CRC Handbook of Chemistry and Physics.

Electron affinity (kJ mol-1)The
energy released when an additional electron is attached to the neutral atom and
a negative ion is formed (where several isotopes exist, a value is presented
for the most prevalent isotope). *

Electronegativity (Pauling scale)The
degree to which an atom attracts electrons towards itself, expressed on a
relative scale as a function bond dissociation
energies, Ed in eV.
χA - χB
=(eV)-1/2sqrt(Ed(AB)-[Ed(AA)+Ed(BB)]/2),
with χH set as 2.2 (where several isotopes
exist, a value is presented for the most prevalent isotope).

1st Ionisation energy (kJ mol-1)The minimum energy required to remove an electron
from a neutral atom in its ground state (where several isotopes exist, a value
is presented for the most prevalent isotope).

Covalent radius (Å)The
size of the atom within a covalent bond, given for typical oxidation number and
coordination (where several isotopes exist, a value is presented for the most
prevalent isotope). ***

Atomic data

Atomic data

Atomic radius, non-bonded (Å)

1.97

Covalent radius (Å)

1.42

Electron affinity (kJ mol-1)

183.3

Electronegativity (Pauling scale)

2.0

Ionisation energies (kJ mol-1)

1st

811.828

2nd

-

3rd

-

4th

-

5th

-

6th

-

7th

-

8th

-

Mining/Sourcing Information

Data for this section of the data page has
been provided by the British Geological Survey. To review
the full report please click here or please look at
their website here.

Key for
numbers generated

Governance indicators

1 (low) = 0 to 2

2 (medium-low) = 3 to
4

3 (medium) = 5 to 6

4 (medium-high) = 7
to 8

5 (high) = 9

Reserve distribution (%)

1 (low) = 0 to 30 %

2 (medium-low) = 30
to 45 %

3 (medium) = 45 to 60
%

4 (medium-high) = 60
to 75 %

5 (high) = 75 %

(Where data are unavailable an arbitrary
score of 2 was allocated. For example, Be, As, Na, S, In, Cl,
Ca and Ge are allocated a score of 2 since reserve
base information is unavailable. Reserve base data are also unavailable for
coal; however, reserve data for 2008 are available from the Energy Information
Administration (EIA).)

Production
Concentration

1 (low) = 0 to 30 %

2 (medium-low) = 30
to 45 %

3 (medium) = 45 to 60
%

4 (medium-high) = 60
to 75 %

5 (high) = 75 %

Crustal
Abundance

1 (low) = 100 to 1000 ppm

2 (medium-low) =10 to
100 ppm

3 (medium) = 1 to 10 ppm

4 (medium-high) = 0.1
to 1 ppm

5 (high) = 0.1 ppm

(Where data are unavailable an arbitrary
score of 2 was allocated. For example, He is allocated a score of 2 since
crustal abundance data is unavailable.)

Explanations
for terminology

Crustal Abundance (ppm)

The abundance of an
element in the Earth's crust in parts-per-million (ppm) i.e. The number of atoms of this element per 1 million
atoms of crust.

Sourced

The
country with the largest reserve base.

Reserve distribution (%)

This is a measure of the spread of future
supplies, recording the percentage of a known resource likely to be available
in the intermediate future (reserve base) located in the top three countries.

Production Concentrations

This reports the percentage of an element
produced in the top three countries. The higher the value, the larger risk
there is to supply.

Political stability of top producer

The World Bank produces a global percentile
rank of political stability. The scoring system is given below, and the values
for all three production countries were summed.

Relative Supply Risk Index

The Crustal Abundance, Reserve distribution (%), Production Concentration and Governance Factor scores are summed
and then divided by 2, to provide an overall Relative Supply Risk Index.

Supply risk

Supply risk

Relative supply risk

Unknown

Crustal abundance (ppm)

0.0000000002

Recycling rate (%)

Unknown

Substitutability

Unknown

Production concentration (%)

Unknown

Reserve distribution (%)

Unknown

Top 3 producers

Unknown

Top 3 reserve holders

Unknown

Political stability of top producer

Unknown

Political stability of top reserve holder

Unknown

Oxidation states and isotopes

Key for Isotopes

Half Life

y

years

d

days

h

hours

m

minutes

s

seconds

Mode of decay

α

alpha particle emission

β

negative beta (electron) emission

β+

positron emission

EC

orbital electron capture

sf

spontaneous fission

ββ

double beta emission

ECEC

double orbital electron capture

Terminology

Common Oxidation states
The oxidation state of an atom is a measure of the degree of oxidation of an atom. It is defined as being the charge that an atom would have if all bonds were ionic. Free atoms have an oxidation state of 0, and the sum of oxidation numbers within a substance must equal the overall charge.

Important Oxidation states
The most common oxidation states of an element in its compounds.

Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.

Oxidation states and isotopes

Oxidation states and isotopes

Common oxidation states

6, 4, 2

Isotopes

Isotope

Atomic mass

Natural abundance (%)

Half life

Mode of decay

209Po

208.982

-

128 y

α

210Po

209.983

-

138.4 d

α

Pressure and temperature - advanced terminology

Specific heat capacity (J kg-1 K-1)

Specific heat capacity is the amount of energy needed to change the temperature of a kilogram of a substance by 1 K.

Young's modulus (GPa)

Young's modulus is a measure of the stiffness of a
substance, that is, it provides a measure of how difficult it is to extend a
material, with a value given by the ratio of tensile strength to tensile
strain.

Shear modulus (GPa)

The shear modulus of a material is a measure of how
difficult it is to deform a material, and is given by the ratio of the shear
stress to the shear strain.

Bulk modulus (GPa)

The bulk modulus is a measure of how difficult to compress a substance. Given by the ratio of the pressure on a body to the fractional decrease in volume.

Vapour Pressure (Pa)

Vapour pressure is the measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system.

Help text not available for this section currently

History

History

Uranium ores contain minute traces of polonium at levels of parts per billion. Despite this, in 1898 Marie Curie and husband Pierre Curie extracted some from pitchblende (uranium oxide, U3O8) after months of painstaking work. The existence of this element had been forecast by the Mendeleev who could see from his periodic table that there might well be the element that followed bismuth and he predicted it would have an atomic weight of 212. The Curies had extracted the isotope polonium-209 and which has a half-life of 103 years.

Before the advent of nuclear reactors, the only source of polonium was uranium ore but that did not prevent its being separated and used in anti-static devices. These relied on the alpha particles that polonium emits to neutralise electric charge.

Podcasts

Podcasts

Chemistry in Its Element - Polonium

(Promo)

You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry.

(End promo)

Chris Smith

Hello, this week in Chemistry in its Element the story of a substance that was named to snub Russia, power space probes keeps paper static free and has even been used as a murder weapon in London. To reveal the secrets of Marie Curie's element, and that's Polonium, here's Johnny Ball

Johnny Ball

Polonium, (element 84), was discovered in 1898 and named after Poland, the homeland of Marie Curie (Ne Sklodowska) who found it with her husband Pierre Curie. This loyalty was a direct affront to Russia who had dominated Poland for so long. The only way she could become educated whilst a teenager, was by risking imprisonment by the Russians by attending secret underground schools, which had to change locations every couple of days. It was only by escaping to Paris, following her older brother and sister, that she was able to forge a career. She was so poor in the early years in Paris, that she sometimes fainted through lack of food. Still she worked tirelessly.

In 1894 she met Pierre, who had made a name for himself in discovering piezoelectricity and was one of her lecturers. They married in July 1895. She wore a black dress as it would be serviceable for her work in the laboratory. They did not exchange rings, but bought each other a bicycle, on which they honeymooned.

X rays had been discovered by Roentgen (Nov 95) and Uranium radiation by Becquerel (Feb 96) in Paris. Working with him (98), Marie coined the phrase "radio activity" and decided to make this here object of study, because no one else was doing it. They realised that radiation was coming from the very atoms and that this was a sign of the atoms breaking up. Only by studying the break up of atoms through radiation, were scientists able to clearly understand how atoms are made up. For this the Curies and Becquerel shared the Nobel Prize for Physics in 1903.

The discovery of Polonium (July 98) was no mean task. Pitchbende, a Uranium bearing ore, seemed to be far to radio active than could be accounted for by the Uranium. The couple got the waste ore free, after the Uranium had been removed. They sieved and sorted by hand, ounce by ounce, through tons of pitchblende before tiny amounts of Polonium were discovered. With the Polonium extracted, there was clearly something far more radio active left behind and soon they had isolated the much more important element Radium (Dec 98), which they so named as it glowed in the dark.

Pierredied in a tragic accident in 1906, which may have been the result of the pain he was in through radiation burns and sickness. (More on this if you wish) For discovering Polonium and Radium, Marie received the Nobel Prize for Chemistry in 1911, becoming the only woman to receive two such prizes.

Natural Polonium Po - 210, is still very rare and forms no more than 100 ?g per ton of Uranium ores. As well as Po - 210, Isotopes Po -211 - 212 - 214 - 215 - 216 and - 218 all occur in the chains of radio active elements, as they decay to form Lead Pb -208. However, they exist for very little time indeed, Po 212 comes in two forms, one having a half life of 45.1 seconds and the other of 300 nanoseconds (300/1,000,000,000ths of a second).

Because it is so rare, Polonium is made by first making Bismuth (also found in pitchblende). Bismuth -209 is found and then artificially changed to Bismuth -210 which then decays to form Polonium -210.

Polonium has a position in the periodic table that could make it a metal, a metalloid or a nonmetal. It is classed as a metal as it's electrical conductivity decreases as it's temperature rises. Because of this property it is used in industry to eliminate dangerous static electricity in making paper or sheet metal.

Because of its short half life, it's decay generates considerable heat (141 W per gram of metal). It can be used as a convenient and very light heat source to generate reliable thermoelectric power in space satellites and lunar stations, as no moving parts are involved.

Chris Smith

Johnny Ball lifting the lid on the radioactive element polonium discovered by Marie Curie and her husband Pierre. Next time on Chemistry in its Element we remain radioactive much like the substance itself with earth scientist Ian Farnan.

Ian Farnan

Anyone familiar with the iconic image of the mushroom cloud understands the tremendous explosive power of a correctly controlled detonation of plutonium. The energy density is mind-boggling: a sphere of metal 10 cm in diameter and weighing just 8 Kg is enough to produce an explosion at least as big as the one that devastated Nagasaki in 1945.

Chris Smith

Ian Farnan with what promises to be an explosive edition of Chemistry in its Element next week. I'm Chris Smith, thank you for listening and see you next time.

(Promo)

Chemistry in its elementis brought to you by the Royal Society of Chemistry and produced by thenakedscientists dot com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld dot org forward slash elements.

We discover how to extract lead from lead(II) oxide. We mix lead(II) oxide with charcoal powder and then heat the mixture using a Bunsen burner. It glows bright red as a reaction occurs and after a fe...

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